Interfacial characterization of dissimilar-metals bonding between vanadium alloy and Hastelloy X alloy by explosive welding

Dissimilar-metals bonding between V-4Cr-4Ti and Hastelloy X alloy was investigated by explosive welding, which is essential to connect coolant pipes of Flibe blanket and external components such as tritium extractor and heat exchanger in fusion reactor. The nano-indentation hardness and corresponding microstructure at the interface are evaluated. After the explosive welding, a characterization of the typical wavy interface indicates good weldability. Discontinuous vortex regions appear at the interface and reveal obvious hardening up to 806 HV. Microstructural analysis indicates that the interlayer consists of Ni37.1V21Cr20.5Fe15.4Mo4.4Ti1.0 Co-0.6 with a fcc lattice structure and a high density of dislocations, and no intermetallic forms. Based on the compositions, the formation of solid solution was predicted by the entropy and enthalpy of the multi-component alloy system, despite the phase diagrams of binary alloys of the constituent elements indicating the formation of intermetallics. Study of hardening mechanism at the interlayer indicates that obvious hardening is mainly attributed to solid-solution hardening and dislocation hardening. (C) 2020 Elsevier B.V. All rights reserved.